Remove the old ARM code generator from ART's Optimizing compiler.

The AArch32 VIXL-based code generator has been the default
ARM code generator in ART for some time now. The old ARM
code generator does not compile anymore; retiring it.

Test: test.py
Bug: 63316036
Change-Id: Iab8fbc4ac73eac2c1a809cd7b22fec6b619755db
diff --git a/compiler/optimizing/intrinsics_arm64.cc b/compiler/optimizing/intrinsics_arm64.cc
index aec1ec7..5691dd0 100644
--- a/compiler/optimizing/intrinsics_arm64.cc
+++ b/compiler/optimizing/intrinsics_arm64.cc
@@ -2738,7 +2738,7 @@
         // TODO: Also convert this intrinsic to the IsGcMarking strategy?
 
         // SystemArrayCopy implementation for Baker read barriers (see
-        // also CodeGeneratorARM::GenerateReferenceLoadWithBakerReadBarrier):
+        // also CodeGeneratorARM64::GenerateReferenceLoadWithBakerReadBarrier):
         //
         //   uint32_t rb_state = Lockword(src->monitor_).ReadBarrierState();
         //   lfence;  // Load fence or artificial data dependency to prevent load-load reordering